FIG. 1 is a schematic diagram of a multi-input multi-output (MIMO) antenna system. As shown in FIG. 1, the MIMO antenna system comprises a plurality of transmitting antennas and a plurality of receiving antennas. Each transmitting antenna sends the data stream independently in the case of the spatial multiplexing, so that the ideal data transfer rate of the N×N MIMO antenna system can be N times as large as that of the SISO (single input single output) antenna system. However, the actual data transfer rate of the MIMO antenna system cannot achieve the ideal data transfer rate. In addition to the space propagation environment, the performance of the wireless terminal as the receiving terminal of the MIMO antenna system has a significant influence on the data transfer rate.
The method for testing the performance of the wireless terminal is need in one controlled environment propagation. Currently, there are three methods used.
(1) Reverb darkroom method: the wireless terminal is placed in the reverb darkroom without anechoic materials for testing. However, there are some problems: the number of the spatial channel propagation models is limited; and the antenna pattern of the wireless terminal cannot be obtained.
(2) Multi-probe method: a multi-probe channel simulator and a plurality of testing antennas surrounding the wireless terminals are used to simulate the spatial channel propagation model. However, there are some problems: the cost of the whole testing system is very high, and the calibration operation is complex.
(3) Two-stage method: FIG. 2 is a schematic diagram of a testing system using a two-stage method. As shown in FIG. 2, the process is divided into two Stages.
Stage 1: a plurality of antenna patterns of a plurality of antennas of the wireless terminal (MIMO DUT as shown in FIG. 2) are obtained using the testing system of the SISO antenna system.
Stage 2: the plurality of antenna patterns are fed to the channel simulator to output testing signals, and the testing signals are sent to the wireless terminal via a cable.
However, there are some problems: the testing process is divided into two discrete steps, so the implementation process is cumbersome; with the conductivity measurement using an RF cable, the actual testing state of the wireless terminal is changed, so the measurement result is inaccurate.